Thick matter pumps of this type are mainly utilized for conveying of concrete and more or less viscous sludge. The pipelines of the thick matter pump and of the material feed containers must therefore be emptied and cleaned at the end of a conveying operation. The conveyor pipeline, which in concrete pumps is usually fastened on a distributor mast, can be emptied either by sucking the concrete contained in it back into the material feed container through the thick matter pump itself or under pressure applied in reversed direction with the help of a pressure medium, like compressed air or water, forced into the conveyor pipeline. The physical wiping of the pipelines is done by means of elastomer sponge balls or cleaning members, which are either sucked through the open conveyor pipe end to the material feed container or are forced through suitable pipeline armatures into an opposite direction. It is furthermore known to provide closable cleaning apertures in the pipeline wall in the area of the swivelling pipe, through which apertures access to the inside of the pipeline for cleaning purposes is possible. Not yet satisfactorily solved is the problem of the emptying of the residual concrete existing in the material feed container. Also the handling of the sponge balls during the cleaning of the pipelines leaves much to be desired.